Field of the Invention
This invention relates to the synchronization of clocks and the detection of clock phase differences, and more particularly to a phase detector circuit and a combination of such circuits to detect phase differences between two clock phases.
In the design of phase detectors for the detection of phase differences between clock phases in high speed clocks, it is desirable to avoid the use of phase lock loops. Various types of phase detectors employing digital latches have been designed to accomplish this purpose. Motorola commercially sells two phase detectors designated as MC12040 and MC 4343/MC4044 which employ digital latches. The phase detector of the MC12040 product and the detector of the present invention both detect phase differences on the leading edge of the input clock signal. The phase detector of the present invention, however, has a number of improvements which give it decided advantages. An inherent feature of the phase lock loop is that it relies on the time average of the phase detector output signals and cannot, therefore, respond to a single out of phase occurrence of two signals. A second characteristic of phase detectors in a phase lock loop application is that they act to control the frequency of the second or non-reference signal.